That I am aware of, there is no option for a rear locking diff (from the factory) on a Ram HD (with the exception of the PW -- which has a 1k lb payload - eg you don't want to be towing with it). The Ram HD also has like 3.5-4" less leg room in the rear -- which may seem insignificant until you sit in it. You can, of course, get the mega-cab but then you've got a longer truck and most of the mega space is really behind the back seat.
Those were major reasons I went to Ford. Now, Ram is supposedly adding the DT cab to the HD in 2023 so all the interior issues may go away next MY.
I don't know if they'll have a locker option -- you'd think the success of the Tremor would have inspired them to compete already -- maybe '23 they will.
Ram did go back to the CP3, though, so there's that.